Sand dunes form as a result of windblown sand piling up behind minor obstacles. Once started, the dune itself becomes an obstacle to windblown sand, and the accumulation of more sand causes the dune to grow. Dunes and dune ridges along the Georgia coast normally grow 10 to 12 feet in height, occasionally much higher, and acquire distinct shapes characterized by gentle windward and steeper leeward slopes. Surface ridges parallel the dune ridges at right angles to the wind.

At the high tide line the foredunes, or primary dunes, begin. This is a fragile area, and one of the most important on the barrier islands. The low foredune acts as the initial barrier to storm waves. In front of these foredunes on incipient dunes grow pioneer plants, such as sea rocket, orach, beach croton, Russian thistle, fiddle leaf, morning glory and the rarer railroad vine. On top of and between the primary dunes, grasses, such as salt meadow cordgrass, bitter panic grass, dropseed grass and sandspur, grow among the pennywort, beach elder and prickley-pear cactus. In these areas, the sand has little or no decaying organic matter. Essential nutrients for these plants are gleaned from the seawater spray that seeps into the sand with the rain. The primary dunes offer harsh living conditions because of the salt spray, quick water drainage, shifting sand and incessant sun exposure. This area is often considered the desert of the beach. Many resident plants have developed adaptations similar to desert plants, such as thick succulent leaves that store water and reduce leaf surface evaporation. Some plants have deep taproots, which extend to the water table, and others have extensive fibrous root systems that spread throughout the dunes to catch the rain that quickly filters through the sandy soil. In some species, individual plants are interconnected by underground stems or rhizomes that spread over great areas of ground, furthering the chances of survival in the face of the harsh and unstable environment. As in the desert, a number of dune animals are active at night and live in burrows during the day to avoid the intense heat and light.

Eventually, sea oats establish themselves in this area. Sea oats are the most important dune stabilizing plant on Georgia’s coast. The long, curly leaves and tall oat heads trap wind-blown sand, burying themselves and neighboring plants under the growing dunes they create. By a process of growing new leaves and roots ahead of the accumulating sand, the sea oats continue to survive while other plants of the evolving community suffocate, degrade and provide humus for the growing oats. This is why almost pure stands of sea oats often thrive on top of well-established dunes. The handsome plants frequently grow six feet tall. They are a golden green in summer and turn light brown in winter. The plant drops spikelets from its plumes in autumn and early winter, which are rapidly disseminated by the wind. Spikelets falling on sites of sand accretion are rapidly buried. Seedlings are produced in the spring and become established during the first growing season. During the second season, extensive tillering occurs, which enlarges the colony. For several years thereafter, plants put on vigorous growth followed by flowering. Rabbits, song sparrows, red-winged blackbirds and cotton mice eat the seeds of sea oats. Cotton mice run from one clump to another feeding on these seeds. Their tracks can often be found among the dunes in early morning.

Dunes stop growing taller when they are so high that wind can no longer blow sand to the top of them. New dunes then form to the windward side. Thus, the biggest dunes are farthest inland, sheltering the forest behind.

The composition of the sand from a dune provides a contrast to the sand near the water line on the beach. The grains are finer and more consistently sorted by the action of the wind moving the sand from the beach to the dunes. The dark, extremely fine grains are the “heavy minerals” so called because they weigh considerably more than quartz grains of the same size. Wind and wave action frequently sort these minerals and concentrate them into distinct patterns. Large deposits of these minerals are mined commercially in the coastal plain terraces as important economic minerals.

The area behind the primary dunes but in front of the larger back dunes is knows as the interdune meadow. A variety of grasses, weeds and woody plants grow here. The types of plants vary greatly from beach to beach, depending on the size of the meadow and the content of humus and clay in the soil. Common interdune plants are camphorweed, wild bean, butterfly pea, pennywort, dune primrose, yucca, grass-leaf, golden aster, spurge-nettle and the dramatic red and yellow firewheels.

The back dunes, sometimes 40 and 50 feet high, are the most striking landforms on the barrier islands. When sand on the windward slope is not anchored by vegetation, it is continually carried over the top by wind and deposited on the lee side, resulting in migrating or “marching” dunes. Dunes may protect the forest during its formation only to bury it later. Many landward migrating dunes on Cumberland Island, for example, are inundating freshwater areas, such as Lake Whitney and Sweetwater Lake, burying critical habitat for alligators, amphibians, otters, wading birds and other animals. The extent of the unstable dune system on Cumberland is primarily due to the free-ranging livestock. These animals grazing and trampling the dunes over the years has caused the elimination of dune stabilizing plants. Continued grazing, human activity and other disturbances accelerate dune erosion. Even partially vegetated dunes are in jeopardy. Storms may breach the dunes, especially where erosion has occurred, creating breaks (called blowouts), and unstable terraces and damaging trees and shrubs.

The salt marsh, such as that to be found on the Georgia Coast, is the most valuable land in the world to the common good of man. Aside from its aesthetic value, it is valuable in three different aspects. First, the salt marsh is the most productive of any known eco-system. A healthy marsh can produce as much as 20 tons of dry matter per year and thus provide food for infant shrimp, oysters, clams and the young of many species of fish. The marsh is also important as an oxygen generator and for the important role it plays in water purification. Georgia has about one-third of the salt marsh on the east coast, and Georgia and South Carolina together have about 50 percent of the salt marsh on the east coast.

The tall, broad-bladed grass that dominates the marsh is smooth cordgrass, Spartina altiniflora, called simply spartina by most marsh lovers. Sometimes growing to be 10 feet tall, it has a thick stalk almost one-half inch in diameter and long tapering leaf blades. This is the great producer of the salt marsh. Cordgrass, inundated at nearly every high tide, has the ability to pull fresh water out of the sea by means of a special root membrane. Some salt still manages to bypass the membrane; too much salt in the plant would eventually kill it. Unique glands are scattered on the surface of the cordgrass to help pluck the remaining salt out of sap and discharge it in a concentrated solution through special pores leading to the outside of the leaf. The solution evaporates, leaving the leaf frosted by salt crystals in the sun until the next high tide.

Plants of the marsh sort themselves into zones, depending on how much tidal water they need to survive. Cordgrass itself occupies the lower level, which receives water and minerals twice daily as the tide comes in. At just a little higher elevation, grow zones of glasswort. This has a green to pink, thick, fleshly stem and virtually microscopic leaves. The little stems are edible and have a crunchy, salty taste. Glasswort is not a grass, but a member of the pigweed family.

At an elevation half-an-inch higher than glasswort is Juncus roemarianus, the black rush of brackish habitat. It is a slow-growing plant with tube-like leaves that are as sharp as needles. Black rush receives tidal water and minerals monthly when the spring tide comes in.

One reason a farmer can grow about seven tons of dry matter, such as corn, on a fertile acre of ground is that he allows only one kind of plant to grow there. This cultivation of one crop, like corn or soybeans, to the exclusion of all others is called “monoculture.” It is the most prominent aspect of successful modern agriculture. The most productive natural ecosystems tend to develop along this same principle like the salt marsh with its cordgrass.

But there are other factors that contribute to high productivity in the salt marsh. No farmer can provide his crop with new water and fertilizer as efficiently as the twice-daily tide does the job. The tide also serves as the agricultural agent by harvesting the nutrient-loaded organic debris, which contributes so much to the food supply of animals that live in the estuaries and near the shore.

Of course there are animals in the salt marsh, too. A whole host of migrant birds, such as the ring-billed gull, feed in the marshes as transients. Perhaps more spectacular are the permanent residents like the clapper rail. More than any other bird, clapper rails symbolize East Coast salt marshes. A clapper rail is frequently heard but rarely seen for its days are spent among the dense stands of cord grass. Lucky observers may catch a glimpse of the “marsh hen,” as it is called, poking its way along a tidal bank. It has a grayish-brown back, light under parts and a long slender bill. The voice of the clapper is a loud, distinctive raucous “kek-kek-kek-kek-kek-kek.” Its voice is soon followed by another and another until it seems the marsh is alive with their calling.

By far, the most numerous animals in the marsh are fiddler crabs. Each crab lives in its own tiny burrow, which is several feet deep. They scurry about stuffing themselves with nutrient-rich marsh mud. While the female fiddler has two claws of equal size, the male has one small claw and one big one, which is almost as large as the rest of his body.

The small meandering rivulets, or creeks, found in the marsh are teaming with living things. The “fry” of shrimp, crabs, and fish, though usually hatched at sea, make their way to these shallow, protected nutrient-rich streams to feed and grow large enough to survive at sea. More than 70 percent of the fish and shellfish that are harvested from the waters of Georgia and South Carolina depend on the salt marsh during some or all of their life cycle. Eighty to ninety percent of the fish gathered for the world market come from similar shallow coastal marshes.

The strong odor of the marsh is caused by the richness of the marsh mud. Since the marsh is regularly covered with tidal water, the organic material in the mud can only be decomposed by anaerobic bacteria, that is, bacteria that take their oxygen from the water. Part of the odor of the marsh is hydrogen sulfide produced as a by-product of these types of bacteria. The blue-green algae that grows at the base of a cordgrass stalk also contributes to the strong marsh smell. This primitive plant has the vital ability to change atmospheric nitrogen into forms that cordgrass and other plants can use.

The southern tip of Jekyll Island is the nicest beach in Georgia that folks can reach easily by car. There are no motels – only a couple of cottages dot the two-mile expanse of beaches and dunes that curves around the end of the island. Shore birds often congregate here, and the forests and white bluffs of Little Cumberland Island can be seen distinctly on the southern horizon. The best place to park is in shady St. Andrews Picnic Area on the southwest corner of the island. It’s rarely crowded, often almost deserted, and it allows beachcombers a good view of the marshes as they begin their walk south and east toward the ocean front beach. The South Picnic Area, which faces the ocean on the southeast side of the island, is another good place to begin a beach walk. Beachcombers who begin here should walk south and west, around the southern tip of Jekyll.

Unfortunately, the beaches north of Jekyll’s southern tip are much narrower and not nearly as nice. Much of the island’s protective barrier of sand dunes was bulldozed by misguided developers in order to make room for beachfront motels after the place became a state park in 1954. This distorted Jekyll’s beach structure, making the beaches much more vulnerable to erosion, which has taken its toll on the island’s northeast shore. Jekyll’s southern, natural treasures on an abused island deserve careful protection by the state of Georgia.

Layering and ripples are the two most common beach structures that the beach walker will observe. Ripples are formed in the near-shore area by both waves and currents. They mark the path of water from the beach back into the ocean. The size of ripples varies widely, but their crests are usually parallel to the beach slope. Layering is the wavy patterns of lighter and darker sand or sand of different textures. It looks something like chocolate swirl ice cream. It’s caused by concentration of heavy minerals or by variations in the size of sand grains. Geologists identify layering and ripples in ancient sandstones to develop new clues to the history of the earth.

The beach never looks the same way twice. The turbulence in the breaker zone and the swash of the waves on the beach constantly rearrange sand particles and reshape the shore line. Materials stirred up by waves are deposited as offshore bars just inland from the zone of greatest breakers. Sand grains are repeatedly carried onto the beach by the swash and carried back out again with the backwash. Those factors, combined with the seasonally changing direction of the wind, produces one of the earth’s most dynamic environments.

In these latitudes, the wind is predominantly from the northeast in fall, from the northeast and northwest in winter and from the southeast in spring and summer. The waves tend to come to shore from the same direction the wind is blowing. That means in the winter, the waves arrive on the beach from the northeast, while in the summer, they come from the southeast.

In the fall and winter when the surf is high with a strong northeast wind, the waves scour the sand from the dunes and upper beach and deposit it on the offshore bars and shoals. This produces a narrow, steep backbeach, called a winter beach. It is recognized by a simple concave upward beach face.

During summer when wave energies are lowest, many sand grains are not moved out with the backwash, and there is a net movement of sand landward. Through the action of the wind, the drier sand of the intertidal beach is transported to the backbeach zones and builds the upper beach and dunes. A horizontal bed of sand, called a berm, forms from the foot of the dunes to a pronounced beach ridge at the high-tide mark. The berm area serves as a source of sand for replenishment and growth of the dunes. This broad shallow beach is called a “summer beach.”

During the transition between the winter and summer beach as the storm removed sand is gradually returned from offshore storage by wave action, the beach develops a ridge and runnel system. The ridge is a large, landward migrating crest of sand, and the runnel is the shallow depression landward of the ridge. As the sand moves slowly landward, the ridge structure is welded to the backbeach face and the runnel is filled in and disappears.

The result of this movement of sand back and forth from dunes to offshore bars is a constantly changing profile of the beach.

The intertidal beach, that is, the section of the beach between normal low tide and normal high tide, is wet and its size is subject to the tidal range and to the slope of the beach. Because of its gradual slope and high tidal range, the intertidal beaches of Georgia can extend as much as a quarter mile out to sea. Beaches near inlets may exceed more than a mile during low tide because of shoals.

Due to the effects of wave action and daily inundation by seawater, the diversity of resident life is low on the intertidal beach zone. The majority of residents are found either in burrows or interspersed among the wet sand grains. The burrows of ghost shrimp and several kinds of polychaete worms become exposed at the lower intertidal beach during low tide. Algae living in the sand often color the wet beaches green during certain seasons and weather conditions. Coquina clams and mole crabs moving just beneath the surface of the sand filter feed in the backwash of the surf. Myriads of tiny crustaceans (mostly amphipods) and small worms living in the wet sand (which can be exposed by flushing the sand through a screen) provide food for the sandpipers that busily probe the sand at the edge of the surf with their beaks. Aquatic and terrestrial animals also visit the intertidal beach. Aquatic animals come in with the tide to feed and escape from enemies. Those that die or are left stranded by the retreating tide become food for the many shorebirds, ghost crabs, raccoons, rats and insects.

Along the high tide line, the wave wash often leaves behind windrows of dead cordgrass from the marsh called “marsh wrack.” Marsh wrack provides a moist environment for beach hoppers (amphipods), insects, and microorganisms and becomes a mesh that traps windblown sand and seeds. In this way, the marsh wrack plays a vital role in forming new dunes supporting plant growth.

The one-half-inch to two-inch holes seen at the high tide line and among the foredunes are ghost crab burrows. The burrows can be a yard deep. These sand-colored crabs decrease in size seaward, a ghost crab demographic that may be seen in the decreasing burrow diameter. Occasionally, ghost crabs leave their burrows during the day mainly to moisten their gills in the shallow swash. Hundreds come out at night, moving sideways and foraging in the marsh wrack. They clean the high tide line of carrion. The remains of their dinner can be seen beside their burrows.